The behavior of cantilever steel pipe column under the cyclic loading that simulates seismic forces was analyzed using elasto-plastic FEM. The models analyzed are a simple steel pipe and a steel pipe reinforced by an encasing steel pipe. The results of FEM analysis are compared with those of the experiments. As a result, the following findings are obtained. 1. The effect of material stress-strain relationship on the results of FEM analysis is evident. The comparison of the case using kinematic hardening rule with the case of isotropic hardening rule shows that kinematic hardening rule qualitatively gives better results than isotropic hardening rule regarding the shape of hysteresis loop and maximum load carring capacity. 2. With kinematic hardening rule, it's possible to simulate the shape of hysteresis loop up to maximum load carring capacity and the mode of local buckling. 3. The confining by an encasing steel pipe as seen in the experiment can be simulated by this FEM analysis. 4. It's possible to estimate load carring capacity and δ_m/S_y with FEM analysis in this paper.

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Buckling strength of concrete filled steel tubular columns is calculated in two different ways. One is performed using the tangent modulus theory( Nsc), considering steel portion and concrete portion behave as a one body. The second one is the method of superposed strength in which a simplesum of separately computed buckling load of steel and concrete columns is regarded as a bucklingstrength(Ns+c). By comparing with two strength, the Ns+c/Nsc ratio almost ranges from 0.9 to 1.05.Inconservative differences( Ns+c/Nsc>1.05) are found in case that strength of concrete (csB) and steel tube ( σy) is quite different such as in combination with cσB=900kg/cm² and σy=2.4t/cm² or cσB=300kg/cm² and σy=6.0t/cm².

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To satisfy the plastic deformabilities at beam-to-column welded connections in the type of site welding with wide flats produced by electric furnaces, the absorbed energy at 0°C should be satisfied over 50J at V-notch Charpy test. 8 specimens for the type of shop welding including the details without scallops are prepared and examined. There are 5 specimens made up the wide flats with low impact tougthness. 1 specimen is fractured owing to weld flaw, however 4 specimens are not fractured and meet the requirement of plastic deformabilities

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In this study, attention is mainly focused on the effect of the construction process for prestressing composite girder bridges with external cables. Then, the performance evaluation related to the load-carrying capacity and the deflection control of the prestressing composite girder is carried out based on the analytical results considered with the constructionprocess as well as some geometric parameters, for not only structural design of new prestressed composite girder bridges but also bridge strengthening of old ones. A design concept is discussed in the construction of new bridges based on a parametric study on the effects of the mechanical behaviors, and as an example of an actual application of the design concept, theproposed method are applied on an actual bridge and the results are obtained together with the performance evaluation.

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The fabricated cylindrical pipes are widely used as the column member, since they have effective shape for axial load. Cylindrical pipes have the circumferential residual stress that occured in the fabricated process of the cold-forming work. Additionally, this process gives much effect on the increasing of the yield stress of material, due to strain hardening. In this report, the column strength of cylindrical tubular members that have variable radius-tothickness ratio is analyzed considering circumferential residual stress and increasing of yield stress which are calculated by the proposed equations considering fabricated process.

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A new composite structure for bridge pier with the use of the steel-frame elements has been proposed to reduce construction labor and period. The composite structure consists of concrete and the steel-frame elements which have lateral joints to connect each other and openings to act as shear connectors. For a hollow pier, the steel-frame elements consist of inner and outer plates connected by tie-plates to prevent plates from buckling. In order to investigate the seismic behavior of the composite hollow pier, the cyclic horizontal loading tests were carried out. The experiments indicated that the longitudinal and transverse steel of the elements acted as reinforcing bar and the composite bridge pier showed high ductility under the influence of tie-plate.

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Long-term fatigue behavior of the plate girder flange with a patch-plate-type attachment is investigated. Fatigue cracks are initiated from root gap and toe of transverse fillet weld between an attachment and a flange plate. Then, those two types of cracks join to propagate together, and finaly break down the flange plate. A finite element analysis shows the greater stress concentration at the root gap than that at the weld toe of the transverse fillet welds. Fatigue strength of the plate girder flange with a patch - plate - type attachment is demonstrated to be lower than the JSSC Category - F.

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Non-scallop welding of beam-column connections is effective in improving plastic deformations performance in earthquakes. However, for site welding of a flange to the underside of a beam, weld quality of overhead position is an important issue. We conducted experiments to estabrish appropriate non-scallop methods for ovrehead welding. The arc welding with high speedrotating is already successful for flat narrow gap welding. We report here on its apprication to overhead welding of flanges to the underside of beams, obtaining stable weld penetration in the root section by dispersion of the arc force.

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[in Japanese]

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